1. FIELD OF THE INVENTION
This invention relates to metal filing cabinets and to methods for constructing such cabinets. More particularly, this invention relates to forming very low-cost but sturdy filing cabinets by using prefinished light gauge steel and preferably by using designs and techniques which minimize the variety of steel stock widths that are required while also minimizing the scrap or waste. For example, an entire cabinet and component parts, including the case envelope, drawers, track assemblies and other structural members, may be constructed from only four discrete widths of prepainted, light gauge steel. Yet, despite the use of light gauge steel, e.g., 0.0195 inches or thinner, the cabinet case provides rigid and structurally strong file cabinets. Furthermore, as a result of using the light gauge metal, the cabinet of the present invention may be 20 to 30 percent lighter in weight and steel usage than conventional cabinets. In addition, the use of prepainted or other prefinished metal readily permits a virtually unlimited color selection as well as simulated wood grain and other patterns at a cost significantly less than the cost of creating these same finishes on cabinets which are assembled prior to finishing. This fact in combination with the use of light gauge metal allows the cabinet to be constructed at a cost significantly below that of present techniques while, at the same time, improving structural strength and marketing flexibility.
More particularly, and with respect to the preferred embodiment, each component part of a file cabinet may be stamped from one of only four discrete widths of prepainted sheet metal. These flat blanks are folded as necessary to form the component parts and are assembled into the cabinet structure. The case in particular is assembled by a combination of adhesively bonding and mechanically fastening the component pieces together. The components of the drawer also may be assembled by adhesive bonding or may be secured by mechanical fastening techniques. In comparison to welding or any other method of mechanically fastening metal, adhesive bonding is superior in most instances because it can provide complete or 100 percent attachment between the joined metal surfaces. This, in effect, creates a single part from multiple pieces whereas mechanical fastening or welding between separate pieces of metal only provides small areas of attachment at the sites of the attachments or welds. The components are still separate everywhere else along their interface. Consequently, the present design and method of construction allows lightweight and thin gauge metal to be used and insures a lightweight cabinet of superior strength and rigidity.
2. DISCUSSION OF THE PRIOR ART
Originally, metal filing cabinet case envelopes or shells were made from separate side, top, back and bottom walls welded or otherwise fastened together and then painted on the outside. Drawers were made in much the same manner with the separate bottom, sides and end walls welded or otherwise fastened together. While many filing cabinets are still constructed this way today, alternate methods of assembly have arisen which have allowed manufacturers to construct file cabinets from prepainted or prefinished steel. Because the finish on prepainted steel is ruined if welded, requiring the metal to be repainted, it is highly desirable to avoid welding as the method for assembling the component pieces into a final filing cabinet. One proposed alternative cabinet design employs extruded corner posts with long narrow slots which slidably engage separate, prepainted, rectangular shaped side and end pieces thereby avoiding welding or even riveting the pieces together. Other proposed designs for cabinets or similar structures rely upon folding various portions of a single piece of prepainted metal together and either interlock the portions or use mechanical fasteners. Such designs, however, would not achieve the desirable, low cost, lightweight, simple and high strength characteristics obtained by the present invention.
Forming of appliance housing from prefinished or prepainted metal has been employed by appliance manufacturers for some time. For example, refrigerator cases have been formed in this manner. However, refrigerator housings are typically made of heavy gauge steel and normally have an inner or second shell. This construction provides ample strength to the exterior housing structure.
Adhesively bonding or gluing cabinet case envelopes together is used in the cardboard or hard wood box area. However, cardboard boxes do not have the structural strength nor the exterior appearance found in a metal cabinet. In the case of hardwood boxes, strength is certainly available but limitations as to exterior appearances and weight become significant factors.
Adhesively bonding cabinets of any material raises a manufacturing problem of holding or restraining the cabinet while the adhesive sets. This adds both time and expense to the manufacture of the product by requiring special clamps or vises as well as the labor necessary to install and remove these clamps or vises. The present invention is specifically designed to eliminate a large portion of the assembly problems associated with adhesively bonding metal. To this end, the preferred embodiment employs interfitting components which are wedge fit together and therefore act as self restraining clamps to hold the assembled pieces in position while the adhesive sets to bond the components to one another. The design of the vertical channels allows them to cooperate with the interior corners of the cabinet envelope so that the track assemblies can be wedged into the cabinet to hold the various edges of the envelope side, top and back walls in place while the adhesive bond is set. As a result, an integral component of the cabinet takes the place of a special clamp and does not need to be removed after the adhesive bonding has set thereby saving significant production costs.
In addition to providing this self clamping function, the vertical corner channels provide the cabinet with structural rigidity, ruggedness or impact resistance and strength. This allows the cabinet pieces to be manufactured from thin gauge metal. While the prior art discloses internal posts and corner supports for providing both strength and structural framing to cabinets and other similar hollow structures, these frame members are typically mechanically fastened to the cabinet case. In the present invention, the corner channels are adhesively bonded to the interior surface of the case envelope to provide a complete surface-to-surface attachment. The result of this total bond is to create, in effect, a one piece structure of superior strength and ruggedness in comparison to a structure formed by mechanically fastening multiple pieces together.
A further feature of the present invention and not found in the prior art is that the entire filing cabinet, including the component parts, is constructed from prefinished sheet metal. Painting both sides of a roll of steel is much simpler and certainly less costly than painting the complex shape of a finished cabinet. Moreover, by using prepainted metal, not only is the interior of the cabinet painted, thereby providing a more aesthetically pleasing and better protected finished product, but a wide variety of exterior styles are available including simulated wood grain and an essentially unlimited number of patterns. These types of finishes are extremely costly to put on a completed cabinet and require a high degree of skill to avoid ruining the exterior appearance of the cabinet.
However, not only is the cabinet constructed from prefinished metal, but it is constructed from a very limited inventory of widths of the prefinished metal strips or coils.
Still another factor in reducing the inventory required to assemble these cabinets and, consequently, a factor in reducing the cost of the overall cabinet is that many of the component parts are reversibly or symmetrically designed in order that one part can be utilized in more than one place. For example, the vertical corner channels are identical multisided members which, as a result of the particular cross sectional shape, can be placed in each of the four corners of the cabinet simply by rotating the relative position of the vertical channel. As a result, only one type of corner channel rather than two or four distinct types is required. Moreover, this same vertical channel, when cut to an appropriate length, functions as a horizontal slide track. Consequently, the versatility of the design allows one manufactured shape to be used for at least two separate pieces.
The versatility of the structure is further evidenced by the design of a second drawer track, in this case a roller track, that is interchangeable with the slide track. Both of these drawer tracks, roller or slide, are designed so that each drawer track can function on either the right or left side of the cabinet. As a result, separate right and left side pieces do not need to be constructed.
The versatility of the present design is still further shown in the drawer construction. The design employs a single drawer base unit which accommodates two different drawer fronts. One drawer front, a "box drawer" front, is slightly taller than the base drawer unit and the other drawer front, or "letter drawer" front, is almost twice as tall as the box front and creates a drawer for much larger articles but employs the same drawer base unit. In addition, drawer extensions or holder rails have been designed as an accessory to attach to the base unit and the letter drawer front to create a drawer for hanging files. These holder rails are manufactured from the same width of prepainted steel as the vertical channels but, in the spirit of the present invention, are reversible and symmetrical in the same manner as the drawer tracks so that any one extension can fit on either the right or left side of the drawer base unit.
As can be seen, all of these features reduce the number of parts necessary to manufacture and to provide in inventory. In addition, these features reduce the number of different parts which are required to assemble a completed cabinet and thereby reduce the cost to produce the overall cabinet. More importantly, these features combine to create an inexpensive, lightweight filing cabinet of superior strength.